1. Field of the Invention
The present invention relates generally to individual section glassware molding machines. More particularly, the present invention relates to a cooling system for cooling the parison plunger in the portion of an individual section glassware molding machine in which the parison is formed.
2. Description of the Prior Art
In the formation of glassware it has been common practice to form a blank, or parison, in a parison mold portion of the glassware molding machine, to automatically transfer the parison to a blow mold portion of the glassware molding machine, and then to blow mold the parison into conformity to a blow mold.
In the parison mold portion of the glassware molding machine, a gob of molten glass is deposited into the parison mold; and a parison plunger is pressed into the parison mold, forcing the gob of glass into a parison that has the combined shape of the parison mold and the parison plunger.
The parison mold portion of the glassware molding machine includes a neck ring that is constructed of two neck ring halves, and that forms the finish portion, or threaded neck, of the parison.
It is this finish portion, or threaded neck, of the parison that is used in the blow mold portion of the glassware molding machine to hold the parison as the parison is blow molded to the final configuration of the glassware; and this same finish portion becomes the threaded neck of the completed container.
Since the finish portion, or threaded neck, of the parison is used to hold the parison for blow molding, the finish portion must be cool enough to have the physical properties that will enable it to withstand the blow molding process and still retain dimensional integrity for the completed container; and yet, the temperature of the parison must be sufficiently high to provide a viscosity that will blow mold.
Thus, it has been a problem to provide cooling for the neck ring that will provide mechanical strength and dimensional integrity in the finish portion of the parison while maintaining the remainder of the parison at a temperature that is sufficiently high to allow blow molding.
The parison plunger includes a shank portion that extends upwardly from an end surface and a parison core portion that extends upwardly from the base portion, that progressively reduces in both circumferences and cross sectional area, and that terminates at a nose.
Since the parison plunger decreases in cross sectional area, from the lower part of the parison core portion to the nose, and since the nose of the parison plunger contacts the gob of molten glass first, the upper portion of the parison core portion requires more cooling than the lower part of the parison core portion in order to maintain all parts of the parison core portion within acceptable temperature limits.
If the upper part of the parison core portion runs too hot, molten glass will weld onto the parison plunger, causing the formed parisons to be defective in their interior contour.
However, if the lower part of the parison core portion runs too cool, the parison will be chilled near the finish portion; and the parison will not have sufficient plasticity for the blow molding operation.
Typically, in the prior art, the parison plunger has included a base and an outer shell that has been attached to the base that has extended upwardly from the base. An inner cooling member has been attached to the base and has extended upwardly into the outer shell.
Air has been introduced into a hole in the base. This air has flowed upwardly through the inner cooling member, radially outward from the inner cooling member and into the shell by way of longitudinally spaced rows of circumferentially disposed holes, and out of the base through one or more exhaust holes.
Duggan, in U.S. Pat. No. 3,508,893, shows and describes a cooling system for a parison plunger as described above.
In Sendt, U.S. Pat. No. 3,644,110, a parison plunger includes a chamber having two regions. A volatile vaporization heat-exchange material is successively vaporized in a first region of a chamber, condensed in a second region of the chamber, and returned by capillary action through a capillary material to the first region of the chamber.
Sendt's temperature control of a parison plunger takes place in a closed system within the parison plunger; and so, even though the device of Sendt is ingenious, it has no bearing on parison plungers that are cooled by air flow through the parison plunger, such as the present invention.
In order to overcome the deficiencies in the processes and structural features for cooling glass molding surfaces and the products produced by parison plungers presently used for producing glassware, as well as those used heretofore, it is a principle object of the subject invention to provide improved details and characteristics of the parison, particularly in the core area that is formed by the parison plunger.
A further object of the present invention is to provide means for cooling the parison plunger by providing a plurality of cooling passages in the parison plunger.
Another object of the present invention is to provide a cooling chamber in a one-piece parison plunger by means of merging a plurality of cooling holes, whereby maximum heat transfer is accomplished by the one piece construction.
Another object of the present invention is to provide means for controlling the cooling of the parison plunger to maintain all of the exterior surface of the parison core portion within acceptable temperature limits.
Another object of the present invention is to selectively determine the longitudinal position wherein cooling air enters exhaust-air passages in the parison plunger.
Finally, it is an object of the present invention to increase the allowable operating speeds of glassware producing machines as well as to lower energy costs.